February 26, 2010, 8:34PM

An Aloha couple has admitted photographing themselves sexually assaulting two of the four children in their blended family, including a severely disabled teenage boy on a respirator, according to government court papers made public today.

Michael J. Marceau and Lisa A. Ford were charged last week with sodomy in Washington County. They were charged this week in Portland's U.S. District Court with arranging the children for sexually explicit photos, which were emailed to others.

The case against the couple began in January, when someone in Portland's U.S. Bureau of Indian Affairs office discovered that an employee had been using a government-issued laptop computer to trade child pornography, according to a government affidavit.

The U.S. Department of Interior's Office of the Inspector General opened an investigation, finding that the Indian Affairs employee had traded child pornography with Marceau's email account, according to the criminal complaint.

On Jan. 6, investigators captured a sexually explicit image sent from Marceau to the government employee, showing a little girl next to a man.

Late last week, agents with U.S. Immigration and Customs Enforcement, ICE, searched Marceau's Aloha home, seizing computers and camera gear. He and Ford share the home with his children -- a girl and a boy -- and hers -- a girl and the teenage boy.

"(Ford's son) has been diagnosed with cerebral palsy, epilepsy and mental retardation," according to an affidavit signed Thursday by ICE Senior Special Agent Josh Findley. "He is on a respirator and cannot move on his own."

Agents interviewed Marceau and Ford in separate rooms. The couple acknowledged shooting pictures of themselves in various sex acts with Ford's children, according to Findley's affidavit, and images from those assaults were found on two computers and a Sony camera.

"Ford maintained that she was unaware of any sexual abuse of either of Marceau's biological children," according to the affidavit. "However, Ford admitted that Marceau had surreptitiously taken photographs of some of his oldest daughter's friends through a bathroom window during a slumber party for his daughter's birthday."

Marceau admitted to agents that he traded images of child pornography with at least 15 people using Yahoo! picture sharing, Findley wrote.